WO2005040461A1

WO2005040461A1 - Method and system for selectively coating metal surfaces

Info

Publication number: WO2005040461A1
Application number: PCT/DE2004/002280
Authority: WO
Inventors: Uwe Landau; Rainer Wiedenbeck
Original assignee: OTB Oberflächentechnik in Berlin GmbH & Co.
Priority date: 2003-10-16
Filing date: 2004-10-14
Publication date: 2005-05-06
Also published as: DE10348734A1; ATE374265T1; EP1678351B1; EP1678351A1; DE10348734B4; DE502004005091D1

Abstract

The invention relates to a method for selectively coating metal surfaces, wherein the surface areas that are not to be covered are masked initially with a molten, waxy water-soluble substance, for instance, polyethylene glycol, 1-Hexadecanol, 1-Octadecanol or the like (first masking). After the waxy substance has been allowed to solidify, the metal surface is then selectively or fully coated with an appropriate liquid dielectric fluid or varnish (second masking). The first masking, i. e. the waxy substance, along with the dielectric fluid possibly found thereupon is completely removed from the metal surface with water. The originally waxy masked surface areas which are now free once again can be subjected to a corresponding aftertreatment, for instance, selective galvanic coating. The second masking, i. e. the dielectric coating or varnishing applied, can then be removed completely from the surface, preferably in an appropriate aqueous-alkaline solution or a microphase cleaner. Said second masking can then be preferably subjected to a subsequent cleaning and drying step. In order to achieve better coating results, a corresponding cleaning and drying step can also be carried out before applying the waxy masking substance and the dielectric coating or varnishing. The invention also relates to a selective coating system for implementing the inventive method.

Description

Method and system for the selective coating of metal surfaces

The present invention relates to a method and a system for the selective coating or lacquering of metal surfaces, in particular for masking surface areas which are not to be processed in a subsequent selective electroplating.

The selective coating or lacquering of metal surfaces is particularly important in the manufacture of electrical or electronic components, where it is used for masking surface areas that are not to be processed in the required selective galvanizing steps.

In the simplest case, the metal is coated around the edges by controlled partial immersion in a suitable dielectric or a suitable lacquer. However, no stripes, spots or other structures can be produced on the surface with this. The coating can, for example, also be selectively printed, sprayed on, sprayed on or spread on using a suitable printing, spraying, spraying or coating device. However, this often results in very undesirable disadvantageous paint splashes or paint wetting in the contact area, the so-called “overspray”, which can hardly be avoided in conventional selective paint application processes and represent a major handicap for these processes. The surface areas which are not to be coated can also be used for protection here a suitable mask, such as a thin mask made of plastic or metal, which is removed again after the non-masked areas have been coated.

The object of the present invention is to create a simple, flexible, precise and inexpensive novel selective coating method for metal surfaces. The coating method sought should be particularly suitable for masking surface areas that are not to be machined in a subsequent selective electroplating of metal surfaces. The task also consists in creating a selective coating system for carrying out this process.

This object is achieved according to the invention by a selective coating method according to claim 1 or a selective coating system according to claim 16. Preferred process variants can be found in the associated subclaims. In the selective coating method according to the invention, the surface areas that are not to be coated and optionally later to be galvanized or otherwise processed are coated or masked in a first masking step with a molten, wax-like water-soluble substance. This is chosen such that it solidifies within a short time after application, so that undesired smearing of the applied first masking layer or possible undermining during subsequent processing of the metal surface is reliably avoided. The molten substance solidifies much faster than the drying of a conventional lacquer, so that the desired masking layer can be applied much faster and more precisely than lacquering in a conventional lacquering process.

In practice, 1-hexadecanol with a melting temperature of approximately 52 ° C., 1-octadecanol with a melting temperature of approximately 55 ° C. or mixtures of these two substances have proven particularly useful as waxy masking substances. However, polyethylene glycol (PEG) with an average molecular weight between about 1000 and 35000, in particular between about 8000 and about 12000, can preferably also be used. In practice, polyethylene glycol with an average molecular weight of about 10,000 has proven itself best. Depending on the molecular weight, polyethylene glycol is characterized by a certain melting range. Table 1 below summarizes the respective melting ranges for several exemplary average molecular weights from the specified molecular weight range.

Molecular weight melting range PC) 1000 37 - 40 1500 45 - 50 2000 50 - 52 3000 56 - 59 4000 59 - 61 6000 60 - 63 10000 63 - 65 12000 64 - 65 20000 63 - 66 35000 64 - 66

Table 1 The wax-like substance can be applied to the metal surface to be selectively coated from the molten state in a contact or non-contact manner. In the simplest case, the application can be carried out by simply immersing the metal surface in a first storage or masking container filled with the molten substance. Analogous to selective soldering, the wax-like medium can be applied very selectively by exciting a standing wave. However, the molten substance can also be applied to the areas of the metal surface to be coated, for example, by utilizing capillary forces. This procedure is particularly suitable for the selective coating of hollow parts, tulips or round and square pins. Another possibility is to apply the molten substance to the metal surface by selective brushing or rolling, ie a transfer via a rotating roller. The application can also be carried out by selective spraying on, spraying on or printing on using a suitable spraying, spraying or printing device (for example by screen printing) or a suitable printer system or in a manner known per se.

When the wax-like substance is applied, the surface areas which are not to be coated or to be masked can optionally also be covered by means of a thin mask made of a suitable plastic, such as polyester or polyimide, or a suitable metal, which is pressed onto the surface.

Using the procedure described, desired masking layers of almost any shape can be applied very easily, quickly and extremely precisely with simple masking systems at low cost. The process enables a high degree of flexibility and is particularly suitable for three-dimensional workpieces with a wide variety of geometries, e.g. Sleeves, tulips as well as round or square pencils or three-dimensionally strongly bent parts, suitable, which are difficult to mask with conventional methods. For example, with three-dimensionally bent stamped parts, one-sided areas can be kept free for subsequent galvanic coating, which are not accessible to selective direct coating.

By applying the molten substance according to the invention, it is also possible to reliably prevent harmful paint splashes or paint wetting in the contact area of electrical or electronic components, which represent a major problem in all conventional selective paint application processes. To ensure optimum processing properties, the wax-like substance is preferably heated to a specific, substance-dependent, predeterminable first target processing temperature of, for example, approximately 40-70 ° C. by means of a first electrical heating device and kept within certain temperature tolerances at this target processing temperature. The heating device is controlled as required by an assigned control device which detects and evaluates the temperature signals of at least one temperature sensor which continuously monitors the temperature of the wax-like substance. Particularly when using metal capillaries, the wax-like medium can thus be applied permanently and very selectively to the surface in liquid form, while lacquers in supply lines which are required for selective coating usually dry up very quickly. Even a wax-like medium that solidifies in a storage container is immediately ready for operation again by simply heating it to its target processing temperature. This is not possible with a paint system.

To ensure proper coating, the metal surface to be coated is preferably first cleaned and dried before the wax-like substance is applied.

After the wax-like masking substance has been applied and allowed to solidify, a liquid, fast-drying dielectric or a lacquer, which dries on the metal surface within seconds, is applied as a second masking layer to the surface areas to be coated or painted and not wax-masked. The dielectric or the lacquer is chosen so that it is at least for the time of a possible subsequent further processing of the metal surface, e.g. a selective galvanic coating that is abrasion-resistant, adhesive and chemically stable. It is stable for at least several minutes in acids, bases and electrolytes containing complexing agents and when a current flows through the metal. These requirements are met, for example, with a pigment-free ink containing MEK (methyl ethyl ketone).

The liquid dielectric or the lacquer can be applied selectively only to the surface areas to be coated and not wax-like masked, or - for the sake of simplicity - over the entire surface. When applied over the entire surface, the wax-like masking substance is also coated accordingly. The application can be touching or non-contact. In the simplest case, the metal surface to be coated is simply completely or partially immersed in a storage or coating container filled with the liquid dielectric or the lacquer. However, the liquid dielectric or the lacquer can also be applied to the metal surface in other known ways, for example by spraying, spraying, brushing or rolling.

In this case, the temperature of the liquid to be applied is preferably also set to a predeterminable second target processing temperature by means of a second electrical heating device. Any deviations from this second target processing temperature are also determined by means of at least one temperature sensor, the temperature signals of which are detected and evaluated by a control device electrically connected to the second heating device.

After the dielectric is allowed to dry, the first masking layer, i.e. the wax-like water-soluble substance, with any dielectric or lacquer thereon with water, in particular warm water, is completely removed, so that the pure metal surface reappears at the areas which were masked at first and can then be further treated in the desired manner. This detachment and detachment of the selectively applied wax-like, water-soluble layer (the first masking) not only enables the above-described simple application of a full-surface dielectric coating (the second masking) but also brings about the desired high selectivity.

The detachment of the waxy substance is preferably supported by a strong movement of water. The water, in particular warm water, can be used, for example, in the form of a water jet, in particular a high-pressure water jet. Detachment can also be promoted by exposure to ultrasound. Since the wax-like substances mentioned are highly water-soluble, they can be removed from the surface in a very simple, quick and essentially residue-free manner in the manner described without the use of solvents. In addition, they are also only much cheaper than lacquers and can be applied much more easily and precisely than these. The selective coating method according to the invention thus proves to be extremely advantageous both ecologically and economically in comparison to conventional coating methods. After the waxy substance has been detached, the surface is preferably first treated again in a manner known per se for the subsequent processes.

The now free areas of the metal surface can then be subjected to a desired aftertreatment. They can be selectively coated with metal, for example by a simple electroplating process.

After the after-treatment, i.e. for example after selective electroplating, the second masking layer, i.e. the applied dielectric or the lacquer is finally completely removed again in an aqueous alkaline solution or in a micro-phase cleaner, essentially without residue. Here, in particular, a solution is used which does not chemically attack the metal surface and a galvanic coating applied to it. The removal or removal of the applied dielectric or lacquer is preferably promoted by exposure to ultrasound. However, detachment can also be promoted, for example, by cavitation and the use of a medium capable of cavitation. To improve the quality, any dielectric, paint or dirt particles that may be released are preferably suctioned off by a suction device in order to prevent undesired contamination of the metal surface.

Finally, the processed metal surface is preferably cleaned and dried once more in a suitable cleaning and drying device.

The process sequence according to the invention described is shown schematically again in FIG. 9 using a flow chart.

A selective coating system for carrying out this method according to the invention comprises a holding, guiding or transport device for a metal to be coated, through which the metal is positioned and guided with high positional precision. It also includes a first masking or coating device for the selective application of a molten, wax-like water-soluble substance to the metal surface, a second masking or coating device for the selective or full-surface application of a liquid dielectric or a liquid coating on the metal surface, a water detaching device for detaching the wax-like water-soluble substance from the metal surface, and an associated one Control device for controlling the selective coating process according to the invention.

The first masking or. Coating device comprises in particular at least a first temperature sensor for determining the temperature of the wax-like substance to be applied and a first electrical heating device for heating this substance to a predefinable first target processing temperature. The at least one

The temperature sensor and the electrical heating device are electrically connected to said control device, which detects the temperature signals of the at least one temperature sensor and controls the electrical heating device as a function of the detected temperature signals so that the substance temperature reaches the first target processing temperature and also maintains it within certain tolerance limits. This first target processing temperature or the first temperature target value can be suitably set depending on the wax-like substance used in each case, so that it is in the desired molten state when applied.

The first masking or coating device can comprise, for example, a first spraying or spraying device for the wax-like substance or also a suitable capillary device for applying this substance to the metal surface. However, for example, it can also simply comprise a first storage or masking container for the wax-like substance, into which the metal to be coated can be immersed or is immersed. Furthermore, a first roller, brush or brush device for rolling, brushing or brushing this substance onto the metal surface can be provided. The first masking device can also be a mask device, e.g. a thin plastic or metal mask, for covering or masking the surface areas not to be coated with the wax-like substance. Such a plastic mask can consist, for example, of polyester or polyimide.

The first masking or coating device is preferably preceded by at least one first cleaning and drying device for cleaning and drying the metal surface.

The second masking or coating device can be any device for selective or full-surface application of a liquid dielectric or a liquid coating on the metal surface. For example, it can comprise a second spraying or spraying device, a second roller or brushing device and / or a second storage or coating container for the dielectric or the lacquer, in which the metal to be coated can be immersed or immersed.

The second masking or coating device in particular also comprises at least one second temperature sensor for determining the temperature of the coating material to be applied and a second electrical heating device for heating the coating material to a predefinable second target processing temperature. The temperature signals of the at least one temperature sensor are applied to the control device, by means of which the second electrical heating device is controlled as required depending on the temperature signals.

To favor the detachment process for the wax-like substance, the water detachment device preferably comprises a water jet device, in particular a high-pressure water jet device. In other configurations according to the invention, it can also comprise a first ultrasound device or a first cavitation device.

The water detaching device can be followed by a second cleaning and drying device for cleaning and drying the selectively coated metal surface.

The water release device can be a galvanizing device, such as e.g. a simple dip electroplating device or another device for further processing of the selectively coated or masked metal surface can be connected downstream.

In addition, a second release device can also be provided for the subsequent residue-free removal of an applied dielectric coating or varnish (2nd masking) from the metal surface. To favor the detachment process, this preferably comprises a second ultrasound device or a second cavitation device.

Finally, the second detaching device can be followed by a third cleaning and drying device for cleaning and drying the metal surface. The cleaning and drying devices mentioned are preferably designed to generate an increased drying temperature of a maximum of about 200 ° C. in order to be able to achieve high coating or strip speeds through the shortest possible drying times.

Further details, features and advantages of the present invention result not only from the associated claims - individually and / or in combination - but also from the following description of preferred exemplary embodiments according to the invention in conjunction with the associated drawings. In the drawings, in which the same parts are provided with the same reference numbers, show in a schematic representation: 1a-1f the selective galvanic coating of a thin metal sleeve shown in cross section using capillary forces; 2a-2e the selective galvanic coating of a taped square pin using capillary forces; 3a - 3e the one-sided electroplating of a 3-D part; 4a and the selective application of a wax-like masking by means of a 4b heated capillary;

5a-5f the selective galvanic coating of a metal strip; 6a and a tulip contact shown transversely to the running direction or in the running direction; 6b FIGS. 6c-6g the selective galvanic coating of a tulip contact according to FIG. 6a; 7a-7e a selective galvanic pin coating; and

8a-8e the selective galvanic coating of contact zones in different planes.

1a-1f illustrate the selective coating method according to the invention on the basis of the selective application of a galvanic coating on the inside of a thin metal sleeve 10.

To ensure proper coating, the metal sleeve 10 to be coated is first cleaned in a first cleaning and drying device (not shown) and dried at higher temperatures.

The lower end of the metal sleeve 10, which is to be electroplated, is then brought into contact with a molten wax-like polyethylene glycol (PEG) 14 with an average molecular weight of about 10 ⁴ by means of a holding and guiding device (not shown) in a storage or masking container 12. As already mentioned above, however, polyethylene glycol with a different average molecular weight of about 1 -10 ³ - 35-10 ³ and a melting range of about 37 - 66 ° C. can also be used, as in all of the following exemplary embodiments. However, the storage container 12 can also contain another suitable molten wax-like substance with comparable material properties, such as 1-hexadecanol, 1-octadecanol or a mixture of these two substances.

The polyethylene glycol 14 is held by a (not shown) electrical heating device at a predetermined target processing temperature of a maximum of about 120 ° C. Compliance with this target processing temperature is checked using a (not shown) The temperature sensor in the storage container 12 is continuously monitored, the temperature signals of which are applied to an associated control device (likewise not shown), by means of which the temperature signals are evaluated and the heating device is controlled as required.

The molten polyethylene glycol 14 rises according to FIG. 1 a by capillary forces in the narrow metal sleeve 10, wets the inside of the metal sleeve 10 and forms a hollow meniscus 16.

The metal sleeve 10 wetted with polyethylene glycol 14 is then pulled up again from the storage or masking container 12 according to FIG. 1b, the polyethylene glycol 14 applied on the inside of the metal sleeve 10 rapidly solidifying and a wax-like, solid first masking layer 14 for the subsequent one Application of a dielectric forms.

The above-described masking of workpieces according to the invention by immersing them in a molten wax-like substance 14 and utilizing capillary forces is particularly suitable for hollow parts, tulips and for round and square pins.

After the polyethylene glycol 14 has solidified, the lower end of the metal sleeve 10 is provided with a corresponding dielectric coating 18 over its entire area by briefly immersing it in a storage container (not shown) with an MEK-containing (methyl-ethyl-ketone-containing) pigment-free ink 18 , The correspondingly coated metal sleeve 10 is shown in Fig. 1c.

The MEK-containing ink used is quick enough to dry, sufficiently abrasion-resistant and adherent and also in acids, alkalis, complexing agent-containing electrolytes and in the event of a current flowing through the metal 10 at least for the duration of the subsequent electroplating process, i.e. at least for several minutes, sufficiently stable. However, another suitable dielectric 18 with the corresponding properties can also be used. As already mentioned above, the dielectric coating 18 can also be applied, for example, by means of a suitable spraying or spraying device.

To accelerate the drying process, the dielectrically coated metal sleeve 10 can optionally also be dried in a second drying device (not shown) at higher temperatures. After the application of the dielectric coating 18, the solidified wax-like polyethylene glycol 14 together with the dielectric coating 18 applied thereon according to FIG. 1d is removed without residue by means of a high-pressure hot water jet 20. However, the polyethylene glycol layer 14 can optionally also be removed by immersing the metal sleeve 10 in water and applying ultrasound or cavitation.

The surface areas originally masked with polyethylene glycol and now free again are then galvanically coated or plated with a desired metal, such as gold, silver or tin, in a conventional electroplating device (not shown). 1e shows the lower end of the metal sleeve 10 with the galvanic coating 22 applied.

After the galvanic coating 22 has been applied, the dielectric layer 18 is finally removed from the surface essentially without residue by immersing the metal sleeve 10 in a suitable aqueous solution with microdisperse additives, so that the result is a metal sleeve 10, the lower one of which 1f is selectively galvanically coated on the inside as desired.

The aqueous solution is chosen so that the metal surface and the galvanic coating are not attacked. Detachment takes place under the action of ultrasound from an associated ultrasound device (not shown) or by cavitation in a solution capable of cavitation, e.g. Potash lye, as this significantly accelerates the stripping process.

Finally, the galvanically coated metal sleeve 10 is cleaned with warm water in a third cleaning and drying device and dried at higher temperatures.

The second exemplary embodiment according to the invention shown in FIGS. 2a-2e illustrates the selective galvanic coating of a square pin 24 by means of a roller device 12, 26, 28 using capillary forces.

According to FIG. 2a, the roller device again comprises a storage or masking container 12 filled with molten polyethylene glycol 14 with a heating device 26, through which the polyethylene glycol 14 is placed on its desired Processing temperature of about 63 - 65 ° C is maintained. The heating device 26 is controlled as required by an associated control device (not shown), at which the temperature signals of a temperature sensor (also not shown) are applied to the storage container 12, which is used for the continuous monitoring of the polyethylene glycol temperature.

In the reservoir or masking container 12, a roller 28 rotates clockwise. The lower roller area is in the molten polyethylene glycol 14, so that the roller surface is wetted with polyethylene glycol 14. The left region of the roller surface emerging from the polyethylene glycol 14 thus carries an adhering thin polyethylene glycol layer 14 in the direction of rotation of the roller 28 upwards.

The square pin 24 to be coated is brought into contact with the roller surface in such a way that the adhering polyethylene glycol 14 penetrates through capillary forces into the tightly taped square spaces to be coated and essentially fills them.

After the selective application of the polyethylene glycol layer 14 to the square pin 24 and the subsequent solidification of this layer 14, the square pin 24 is covered with a suitable liquid dielectric 18 according to FIG. 2b by briefly immersing it in a storage, coating or masking container (not shown) the dielectric 18 coated. As already mentioned, the dielectric 18 can, however, also be applied to the entire surface of the surfaces, for example by spraying, spraying or brushing.

After the dielectric 18 has been applied and left to dry, the solidified polyethylene glycol masking layer 14 according to FIG. 2c is removed again without residue from the metal surface by means of a high-pressure hot water jet 20.

Subsequently, the surface areas of the square pin 24, which were originally masked with polyethylene glycol 14 and are now free again, are galvanically coated or plated with a suitable metal layer 22, such as, for example, a gold, silver or tin layer, in a conventional electroplating device (not shown). The correspondingly coated square pin 24 is shown in Fig. 2d. After the galvanic coating 22 has been applied, the dielectric layer 18 is in turn finally detached from the surface essentially without residue by immersing the square pin 24 in a suitable aqueous alkaline solution with / without microdisperse additives, so that the selectively galvanically coated square pin is the end result according to FIG. 2e 24 remains. Detachment takes place here under the action of ultrasound from an associated ultrasound device (not shown), since this can significantly accelerate the detachment process. For better detachment, the dielectric layer 18 can, however, also be subjected to cavitation by means of a cavitation device, ie a cavitation-generating device with a medium capable of cavitation, such as potassium hydroxide solution.

To improve the coating quality, the metal surface can again be subjected to the cleaning and drying steps already described.

The third exemplary embodiment according to the invention shown in FIGS. 3a-3e illustrates the one-sided galvanic coating of a punched part 30 (shown in cross section) bent downwards by means of the roller device 12, 26, 28 according to FIG Clockwise rotating roller 28 is arranged in a heated storage, coating or masking container 12 which is filled with molten polyethylene glycol 14 approximately up to its axis of rotation, so that the left area of the roller surface emerging from the molten polyethylene glycol 14 has an adhering thin polyethylene glycol layer 14 in the direction of rotation of the roller 28 leads upwards, which finally covers the entire upper left quadrant of the roller according to FIG. 3a.

The stamped part 30 to be coated and previously cleaned and dried is guided in the direction of arrow 32 from right to left over the roller 28, the projecting region 30a of the stamped part 30 to be coated on one side facing downward. Its distance from the roller 28 is chosen so that it stripes the polyethylene glycol layer 14 from the roller surface with its lower end. The stripped polyethylene glycol 14 accumulates on the left side of the projecting area 30a to be masked and finally completely covers this, as shown in FIG. 3a.

After the selective application of the polyethylene glycol layer 14 to the stamped part 30 and the subsequent solidification, the stamped part 30 is briefly immersed in a (not shown) storage, coating or masking container with a suitable liquid dielectric 18 according to FIG. 3b coated with the dielectric 18 over the entire surface. As already mentioned, however, the dielectric 18 can also be applied to the surfaces, for example, by spraying, spraying or brushing.

After the application of the dielectric 18, the solidified polyethylene glycol masking layer 14 according to FIG. 3c is removed again without residue from the metal surface by means of a high-pressure hot water jet 20.

Subsequently, the surface areas of the stamped part 30, which were originally masked with polyethylene glycol 14 and are now free again, are galvanically coated with a suitable metal layer 22, such as gold or silver plating, in a conventional dip galvanizing device (not shown). The correspondingly coated stamped part 30 is shown in FIG. 3d.

After the galvanic coating 22 has been applied, the dielectric layer 18 is in turn finally detached from the surface essentially without residues by immersing the stamped part 30 in a suitable aqueous alkaline solution with microdisperse additives, so that the selectively coated stamped part 30 remains as the final result according to FIG. 3e , Detachment takes place here under the action of ultrasound from an associated ultrasound device (not shown), since this can significantly accelerate the detachment process. The dielectric layer 18 can, however, also be subjected to cavitation again by means of a cavitation device for better detachment.

The procedure according to the invention described enables, in particular in the case of three-dimensional workpieces, surface areas on a one side to be kept free for subsequent selective galvanic coating in a simple manner, which are not accessible to conventional, selective direct coating.

In the fourth exemplary embodiment according to the invention shown in FIG. 4, the underside of a metal strip 34 is selectively coated with polyethylene glycol 14. The metal strip 34 to be coated is in this case according to the schematic side view in FIG. 4a in the direction of arrow 32 from right to left at a constant speed above one along the heated capillary device 36, through which the molten polyethylene glycol 14 is applied in a strip-like manner to the metal surface with high precision. The corresponding polyethylene glycol strip 14 in the middle of the metal strip 34 is shown again schematically in the top view according to FIG. 4b. The beginning 14a of the polyethylene glycol strip 14 corresponds to the position of the heated capillary device 36.

The selectively coated or masked metal strip 34 can now be further processed in the manner according to the invention described above. The non-masked two edge regions of the metal strip 34 are in turn first coated or masked with a suitable dielectric 18, for example by simply passing the metal strip 34 through a storage container filled with the dielectric at a certain speed. The wax-like polyethylene glycol masking layer 14 is then detached with warm water 20 essentially without residue. The easiest way to remove them is in a warm water bath under the influence of ultrasound. After the polyethylene glycol layer 14 has been detached, the originally masked and now again free surface strip is selectively galvanically coated or plated with a suitable metal 22. In a last process step, the applied dielectric layer 18 is finally removed without residue in an aqueous alkaline solution. To improve the coating quality, the metal surface can again be subjected to the cleaning and drying steps already described.

5a-5f illustrate in a fifth exemplary embodiment according to the invention the masking and the subsequent selective electroplating of an endless metal strip 38 with gold, silver, tin or the like. As usual, the surface of the metal strip 38 to be coated is first cleaned and dried. The surface areas that are not to be electroplated are then covered or masked with a thin polyimide mask 40. As already mentioned above, a thin mask made of another suitable plastic, e.g. Polyester, or a thin metal mask can be used.

The metal strip 38 is now moved with the masked side down by means of a guide or transport device (not shown) at a constant speed in the direction of arrow 42 from left to right over an electrically heated spray or spray head 44. 5a, the masked underside of the metal strip 38 is coated over its entire surface with molten polyethylene glycol 14, which solidifies like a wax immediately after application. After passing through the spray or spray head 44, the mask 40 is removed from the surface, so that, according to FIG. 5 b, only the non-masked and later to be galvanized surface areas are provided with a solidified wax-like polyethylene glycol layer 14.

Subsequently, the underside of the metal strip 38 is provided over its entire area with a dielectric coating or lacquer 18. This can be applied, for example, by simply spraying on or spraying on a suitable quick-drying dielectric by means of a suitable spraying or spraying device (not shown).

After the dielectric coating 18 has been allowed to dry, the solidified polyethylene glycol mask 14, together with the dielectric 18 applied to it, is removed without residue by means of a high-pressure water jet 20, so that, according to FIG. 5d, only the surface areas originally masked with the mask 40 are selectively dielectrically coated 18 , If necessary, the metal strip 38 could also be passed through a water bath, for example, to detach the polyethylene glycol masking 14 and subjected to ultrasound or cavitation.

The surface areas of the metal strip 38, which were originally coated with polyethylene glycol 14 and are now free, are now processed in a conventional manner, e.g. in a dip galvanizing device, provided with a suitable galvanic coating 22.

Subsequently, the selective dielectric coating 18 is subjected to ultrasound or cavitation in the manner described above and detached from the metal surface essentially without residue by means of a micro-phase cleaner, so that the metal strip 38 with the applied selective galvanic coating 22 remains in accordance with FIG. 5f. As usual, this can then be cleaned and dried in a last process step.

6c-6g illustrate in a further exemplary embodiment according to the invention the industrially extremely important, selective galvanic coating of a contact tulip or a tulip contact 46 transversely to the running direction. 6a and 6b show such tulip contacts 46 transversely to the running direction or in the running direction. The tulip contact 46 is first cleaned and dried again before the contact fingers 46a to be electroplated are brought into contact with molten wax-like polyethylene glycol 14, which is kept in a storage or masking container (not shown) at a specific target processing temperature. The molten polyethylene glycol 14 rises as shown in FIG. 1a by capillary forces between the contact fingers 46a and fills the space between the contact fingers 46a.

After the polyethylene glycol 14 has solidified, the tulip contact 46 masked with polyethylene glycol 14 is completely provided with a corresponding dielectric coating 18 by immersion in a suitable coating bath (not shown). The correspondingly painted or masked tulip contact 46 is shown in FIG. 6d.

In the next process step, the applied polyethylene glycol mask 14 according to FIG. 6e is completely detached from the metal surface again by means of a high-pressure water jet 20 in order to expose the region of the metal pin 14 to be electroplated again. However, the polyethylene glycol mask 14 can also be detached, for example, by immersing it in a water bath and applying ultrasound.

The free surface area of the tulip contact 46 is now provided with the desired galvanic coating 22 in a dip electroplating device (not shown) according to FIG. 6f.

Subsequently, the selective dielectric coating 18 is subjected to ultrasound or cavitation in the manner described above and detached from the metal surface essentially without residue by means of a micro-phase cleaner, so that the tulip contact 46 with the applied selective galvanic coating 22 remains in accordance with FIG. 6g. A qualitatively comparable selective coating of a tulip contact does not allow any other conventional selective coating process. This applies in particular across the direction of travel.

The galvanically coated tulip contact 46 can then, as usual, be cleaned and dried in a final process step. 7a-7e illustrate the selective electroplating of a metal pin 48 in a further exemplary embodiment according to the invention.

The metal pin 48 is first cleaned and dried again before the area to be electroplated is provided with a polyethylene glycol mask 14. The polyethylene glycol mask 14 is applied according to FIG. 7a by means of a felt 50 on the metal surface. However, the metal pin 48 can, for example, also be appropriately masked by means of a suitable roller or roller device.

Subsequently, the masked metal pin 48 is completely provided with a corresponding dielectric coating or masking by immersion in a suitable coating bath (not shown). The correspondingly painted metal pin 48 is shown in Fig. 7b.

In the next process step, the applied polyethylene glycol mask 14 is completely detached from the metal surface again using a high-pressure water jet 20 in accordance with FIG. 7c in order to expose the region of the metal pin 14 to be electroplated again. However, the polyethylene glycol mask 14 can also be detached, for example, by immersing it in a water bath and applying ultrasound.

The free surface area of the metal pin 48 is then provided with the desired galvanic coating 22 in a dip galvanizing device (not shown) according to FIG. 7d.

Subsequently, the selective dielectric coating 18 is subjected to ultrasound or cavitation in the manner described above and detached from the metal surface essentially without residues by means of a micro-phase cleaner, so that, according to FIG. 7e, the metal pin 48 with the applied selective galvanic coating 22 remains. The galvanically coated metal pin 48 can then, as usual, be cleaned and dried in a final process step.

The metal pin 48 cannot be coated as selectively as in the present exemplary embodiment and without a run-out zone by means of no other, cost-comparable conventional selective coating method. 8a-8e finally illustrate, in a last exemplary embodiment according to the invention, the production of contact zones in three different planes of a previously cleaned and dried workpiece or component 52.

The different levels of the component 52 to be electroplated are first of all each provided with a polyethylene glycol mask 14. According to FIG. 8 a, the maskings 14 are applied to the surface with high precision by three heated capillary devices 36. The lengths of the capillary devices 36 are each adapted to the different height of the plane to be coated.

With adjustable nozzles and a corresponding control of the transfer, any pattern, such as dots or stripes, can be produced very selectively. However, the surface areas to be masked can also be provided with a wax-like coating if required.

The underside and the side surfaces of the masked component 52 are then completely provided with a corresponding dielectric coating 18 by immersion in a suitable coating bath (not shown). The correspondingly painted component 52 is shown in Fig. 8b.

In the next process step, the applied polyethylene glycol masking 14 according to FIG. 8c is completely detached from the metal surface again by high-pressure water jets 20 in order to expose the regions of the component 52 to be electroplated for subsequent galvanization. The polyethylene glycol mask 14 can also be removed here, for example, by immersing it in a water bath and applying ultrasound.

The free surface areas of the component 52 are now provided with the desired galvanic coating 22 in a dip electroplating device (not shown) according to FIG. 8d.

Subsequently, the selective dielectric coating 18 is again subjected to ultrasound or cavitation and, using a micro-phase cleaner, is detached from the metal surface essentially without residue, so that, according to FIG. 8e, the component 52 remains with the applied selective galvanic coating 22. The galvanically coated component 52 can then, as usual, be cleaned and dried in a final process step.

Claims

claims

1. A method for the selective coating of metal surfaces, in particular for masking surface areas not to be processed in a subsequent selective electroplating, with the following method steps: masking the surface areas not to be coated with a molten, wax-like water-soluble substance (14); Applying a liquid dielectric (18) to the unmasked surface areas; and detaching the waxy substance (14) with water (20).

2. The method according to claim 1, characterized in that the wax-like substance (14) polyethylene glycol, 1-hexadecanol, 1-octadecanol, a mixture of 1-hexadecanol and 1-octadecanol or a similar water-soluble substance is used.

3. The method according to claim 2, characterized in that polyethylene glycol with an average molecular weight of 8000 - 12000 is used.

4. The method according to any one of the preceding claims, characterized in that the molten wax-like substance (14) by: - Exploitation of capillary forces after contacting the metal surface with this substance (14) or immersion in this substance (14); - spraying, spraying or brushing; Immersing the metal surface in this substance (14); Transfer to the metal surface via at least one rotating roller or roller (28); - a felt (50); and / or a transfer is applied to the metal surface by means of a capillary device (36).

5. The method according to claim 4, characterized in that a standing wave is excited when immersed in the wax-like substance (14).

6. The method according to any one of the preceding claims, characterized in that the surface areas not to be masked when the wax-like substance (14) is applied are covered by a thin mask (40) made of plastic or metal applied to the surface.

7. The method according to claim 6, characterized in that a plastic mask (40) made of polyester or polyimide is used.

8. The method according to any one of the preceding claims, characterized in that the wax-like substance (14) and / or the dielectric (18) to be applied are each heated to a specific temperature by a heating device (26).

9. The method according to any one of the preceding claims, characterized in that the dielectric (18) is applied by spraying, spraying, brushing, rolling or dipping the metal surface.

10. The method according to any one of the preceding claims, characterized in that the dielectric (18) is applied selectively or over the entire surface to the metal surface.

11. The method according to any one of the preceding claims, characterized in that the wax-like substance (14) by means of a water jet, in particular a high pressure water jet (20), is detached.

12. The method according to any one of the preceding claims, characterized in that the wax-like substance (14) is acted upon by ultrasound during detachment.

13. The method according to any one of the preceding claims, characterized in that the metal surface is selectively galvanized after the waxy substance (14) has been detached.

14. The method according to claim 13, characterized in that the dielectric (18) is detached from the metal surface after the electroplating in an aqueous alkaline solution or in a micro-phase cleaner.

15. The method according to claim 14, characterized in that the dielectric (18) is acted upon by ultrasound when detached or in a cavitation-capable medium with cavitation.

16. A selective coating system for metal surfaces comprising: a holding / guiding device for a metal to be coated (10, 24, 30, 34, 38, 46, 48, 52); a first masking or coating device (12, 26, 28, 36, 40, 44, 50) for the selective application of a molten, wax-like water-soluble substance (14); a second masking or coating device for applying a liquid dielectric (18); a water release device (20) for removing the wax-like water-soluble substance (14); and a control device.

17. Coating system according to claim 16, characterized in that the first masking or coating device (12, 26, 28, 36, 40, 44, 46, 48, 52) a first storage or masking container (12), a first spraying (44), spray or brush device, a felt (50), a first roller or Roller device (28), a capillary device (36) and / or a mask (40) made of plastic or metal.

18. Coating system according to claim 16 or 17, characterized in that the second masking or coating device comprises a second storage or coating container, a second spraying, spraying or brushing device and / or a second roller device.

19. Coating system according to one of claims 16 - 18, characterized in that the first masking or coating device (12, 26, 28, 36, 40, 44, 46, 48, 52) and / or the second masking or coating device at least each comprise a temperature sensor and an electrical heating device (26).

20. Coating system according to one of claims 16 - 19, characterized in that the water release device comprises a water jet device, in particular a high pressure water jet device (20) or a first ultrasonic device.

21. Coating system according to one of claims 16 - 20, characterized by one of the water detaching device (20) downstream galvanizing device.

22. Coating system according to one of claims 16-21, characterized by a second release device for removing the dielectric coating.

23. Coating system according to claim 22, characterized in that the second detachment device comprises a second ultrasound device or a second cavitation device with a cavitation-capable medium.

24. Coating system according to one of claims 16-23, characterized by at least one cleaning / drying device for cleaning and drying the metal surface.